1. Field of the Invention
The invention pertains generally to multi-user digital bidirectional communications buses which utilize central bus controllers for traffic direction, and more specifically to the protection of multi-user communications networks from residual design errors in bus user elements.
2. Description of the Prior Art
Avionic systems have progressively been converted from analog-to-digital. This development should continue with microprocessor based design permeating virtually all new avionic product, necessitating proper interfaces between digital boxes to take advantage of the ability to serially transmit vast amount of data over single pairs of interconnecting cables. With such systems significant costs and weight savings can be realized and system reliability can be improved.
Further increases in reliability may be achieved with redundant systems. Redundant multi-user bi-directional communications buses, however, are susceptable to simultaneous disablement due to bus user disign errors. An error common to similar elements, distributed and separated between redundant buses can result in multi-bus disablements. Such errors may be eliminated by thorough testing to seek out and correct design errors. This is an expensive procedure, however, and significantly adds to the cost of the overall system. Significant changes may be realized by designing error tolerant communications networks. Such networks for large numbers of users and many user design variations do not generate high levels of confidence, unless adequately tested. This problem is compounded when similar type user elements are distributed on redundant communications networks, for it is difficult to determine the existence of a low likelihood of multiple network disablements due to a single error that may be cross coupled via common design.
The present invention provides a communications network tolerant to design errors in user elements that permits a modest likelihood that disabling design errors are residual within these elements.